Ensure your ASP.NET Core application can create all it's controllers

When_the_application_is_configured.cs

using FluentAssertions;
using Microsoft.AspNetCore.Mvc;
using Microsoft.AspNetCore.Mvc.Testing;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using System;
using System.Collections.Generic;
using System.Linq;
using Xunit;

namespace MyProject.Tests.Configuration
{
    public class When_the_application_is_configured : IClassFixture<WebApplicationFactory<Startup>>
    {
        private readonly WebApplicationFactory<Startup> _factory;

        public When_the_application_is_configured(WebApplicationFactory<Startup> factory)
        {
            _factory = factory.WithWebHostBuilder(config => 
                config.ConfigureAppConfiguration( (context, builder) =>
                    {
                        // force using local development settings here to ensure valid configuration
                        builder.AddJsonFile("appsettings.json", optional: false, reloadOnChange: false)
                            .AddJsonFile($"appsettings.LocalDevelopment.json", optional: true, reloadOnChange: true);
                    }));

        }

        [Theory]
        [MemberData(nameof(Controllers))]
        [Trait("Category", "Integration")]
        public void It_should_be_able_to_create_all_controllers(Type controller)
        {
            // Arrange
            using var serviceScope = _factory.Services.CreateScope();
            var serviceProvider = serviceScope.ServiceProvider;

            // act
            var service = serviceProvider.GetRequiredService(controller);

            // Assert
            service.Should().NotBeNull($"controllers of type {controller.Name} can be created");
        }

        public static IEnumerable<object[]> Controllers
        {
            get
            {
                // Note that this assumes all controllers are in the same assembly as the Startup class
                return typeof(Startup)
                    .Assembly
                    .GetTypes()
                    .Where(t => typeof(ControllerBase).IsAssignableFrom(t))
                    .Select(t => new object[]
                   {
                        t
                   });
            }
        }
    }
}